Binding of metal ions to amino acids, polypeptides, purines, pyrimidines and other nitrogen-containing bases will be studied using nuclear quadrupole resonance spectroscopy. The 14N nqr spectra will be obtained using the adiabatic demagnetization in the lab frame (ADLF), double resonance method. In addition the nuclear quadrupole resonance spectra of 67Zn (I equals 5/2) and 25Mg (I equals 5/2) in complexes with imidazole, histidine and related substances, and eventually in metalloproteins, will be studied. These studies will permit characterization of the electronic and geometrical environment about the metal of 14N atoms in considerable detail. The binding of B12 related substances to proteins will be studied using 1H and 13C nmr, and using 59Co nqr spectra. On the basis of model system studies it should be possible to determine whether benzimidazole is displaced from bonding to Co in the protein-bound methyl cobalamin.